Ultrasonic waves have been widely used in medical applications, including diagnostics and therapy as well as many industrial applications, e.g., welding, cutting, fiber optics technology, speed meters, etc. Diagnostic use of ultrasound waves includes using ultrasonic waves to detect underlying structures in an object or human tissue. In this method, an ultrasonic transducer is placed in contact with the tissue or object via a coupling medium, and high frequency (1–10 MHz) ultrasonic waves are directed into the tissue. Upon contact with the various underlying structures, the waves are reflected back to a receiver adjacent the transducer. By comparison of the signals of the ultrasonic waves sent with the reflected ultrasonic wave as received, an image of the underlying structure can be produced. This technique is particularly useful for identifying boundaries between components of tissue and can be used to detect irregular masses, tumors, etc.
Three therapeutic medical uses of ultrasound waves include aerosol mist production, contact physiotherapy, and soft tissue ablation. The ultrasound contact physiotherapy procedure may cause a patient significant discomfort and/or pain, and skin may appear raw and damaged. Aerosol mist production makes use of a nebulizer or inhaler to produce an aerosol mist for creating a humid environment and delivering drugs to the lungs.
Ultrasonic nebulizers operate by passing ultrasound waves of sufficient intensity through a liquid, the waves being directed at an air-liquid interface of the liquid from a point underneath or within the liquid. Liquid particles are ejected from the surface of the liquid into the surrounding air following the disintegration of capillary waves produced by the ultrasound. This technique can produce a very fine dense fog or mist.
Aerosol mists produced by ultrasound are preferred because a smaller particle size of the aerosol can be obtained with the ultrasonic waves. One of the major shortcomings of ultrasonic inhalers and nebulizers is that there is no directed aerosol to the target. An air stream is then required to direct the aerosol to the target, but this decreases the efficiency of ultrasound.
Ultrasonic sprayers (Sonic and Materials Inc., Misonix Inc., Sono-Tek Inc., Zevex International, Inc., operate by passing liquid trough central orifice of ultrasound instrument-tip. See, for example, U.S. Pat. Nos. 3,765,606; 4,659,014; 5,104,042; 4,9307,00; 4,153,201; 4,655,393; 5,516,043; 5,835,678; 5,879,364; and 5,843,139.
Ultrasonic inhalers and drug delivery systems from Medisonic USA, Inc., 3M, Siemens Gmb, The Procter & Gamble Company, Sheffield Pharmaceuticals, Aradigm, Inc., operate by atomizing liquid using piezoceramic film. See, for example, U.S. Pat. Nos. 4,294,407; 5,347,998; 5,520,166; 5,960,792; 6,095,141; 6,102,298; 6,098,620; 6,026,808; and 6,106,547.